text:
Why does a missile have small wings but better agility than a plane?
An anti air missile has often very small wings but out performs a fighter aircraft, e.g. much higher g-load, since g-load comes from lift which is the area of wing.
Why not designing an aircraft like a missile? E.g. low drag, high agility.

Aren't fighters already capable of more Gs than the pilots can safely manage? Also being able to land is usually considered a plus for aircraft...

Ability to land and take off, cool, I forgot that.

And there is no wet meat ball inside it.

https://en.wikipedia.org/wiki/Messerschmitt_Me_163_Komet : rocket-powered WW2 fighter. Fastest plane in the air at the time .. for seven minutes, at which point it would run out of fuel. Also horrifyingly dangerous for many reasons such as no landing wheels and corrosive/explosive fuel.

Some aircraft have been designed a bit like missiles, like the Lockheed F-104 Starfighter, but it was a short-lived trend that didn't live long.

@VilleNiemi Generally, no.  My super hornet is structurally limited to 7.5, however, I am capable of more.  More than that, once you start loading ordinance on the aircraft the max G loading further decreases.

@pjc50: If you're looking for something even more topical, how about the Ba-349 "Natter"? ;-)

First of all, a missile is operating at a much higher dynamic pressure than the airplane. After all, it has to catch up with it to do its job. Since dynamic pressure scales with the square of airspeed, the wings of a missile twice as fast as the target would need only a quarter of the wing area to produce the same forces.
Secondly, the missile uses its thrust just as much as the lift from its vanes to change direction in the initial flight phase when the rocket motor runs and the biggest course changes are needed. With an airplane, this is normally not possible, since most planes need to fly in a small range of angles of attack and sideslips to operate properly. Exceeding those will produce substantially more drag and might lead to loss of control.
Lastly, the missile has to carry only the mass for a few seconds of flight. The burning time of a rocket motor is just a few seconds for short-range missiles, and their typical flight time is about 30 seconds. Since they do not need to carry the fuel to return to base, their mass can be held down, which improves agility.

30 second flight time, but only a few seconds' burn? Does that mean the missile is just unguided ballistic for 20+ seconds? If so, wouldn't it be extremely unlikely to strike or even get near its target? Or are the vanes still operating, just not thrust vectoring?

@RileyAvron: It's a guided "glider" for the remainder 20+ seconds of its flight. Remember, electronics and servos don't use rocket fuel - they use batteries.

@slebetman But, in that flight regime, it's not "[using] its thrust just as much as the lift from its vanes to change direction." So I think some clarification is needed.

@DavidRicherby: For clarification I use the Vympel R-73: It can engage targets which fly at the side or even slightly to the rear of the fighter launching it. While the rocket motor runs, it has to massively change its impulse to engage the target. Once that is done, it coasts and needs comparatively small corrections, for which the canard control surfaces are used. BTW, they are not driven by batteries but by a gas generator (better for long-term storage).

Most missiles do not have better agility than planes. The maneuverability of an flight vehicle is defined typically by what is called a "maneuverability graph". Aircraft generally have much better maneuverability than traditional missiles do, but there are some newer missiles that use a technology called "Thrust-Vector Control" which can potentially make the missiles more agile in some, but not all, parts of the envelope. In general missiles achieve their lethality by greater speed, not greater maneuverability.


text:
Can a pilot use their GPS/FMS to fly a VOR or NDB approach?
GPS is more accurate than a VOR or NDB signal.  Can we use a GPS to fly a VOR or NDB approach from the initial approach fix through the missed approach and hold?
I know there are two types of approaches that deal with GPS and VOR/NDBs:

NDB RWY 35L (KCOS RWY 35L) without GPS in the title
VOR or GPS-A (KGUC VOR or GPS-A) with "or GPS" in the title

I'm specifically asking about the first type or approach without the wording "or GPS in the title.

GPS can be more precise, this is not necessarily more accurate or more reliable. There is more involved with determining suitability for a particular end goal. There are locations where the GPS signal is frequently lost (eg a mountain valley) and thus unreliable, there are also differences in ground distance vs slant range DME for holding pattern obstacle clearance and conversion errors with different survey datums.

No, you still have to monitor the underlying NAVAID. You just have to read further in that same section of the AIM. Reference the most recent edition of the AIM, which has Change 3 dated April 27, 2017. In section 1-2-3-c-5 it says:

Use of a suitable RNAV system as a means to navigate
  on the final approach segment of an instrument approach
  procedure based on a VOR, TACAN or NDB signal, is
  allowable. The underlying NAVAID must be operational
  and the NAVAID monitored for final segment course
  alignment.

That last sentence in the quote above is the important part.

To clarify further, the named fixes and named procedures must be included in the GPS receiver's database of published nav data. Using lat and long waypoints or manually connecting waypoints into a procedure is not acceptable for IFR.

In the US they can (Effective: May 26, 2016).
This change allows for the use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure (IAP) based on a VOR, TACAN, or NDB signal. The underlying NAVAID must be operational and monitored for the final segment course alignment.
Still can’t fly an ILS or localizer approaches.
Update: 2017-04-19 Max Trescott has a good explanation of how to use GPS in conjunction with ground-based navaids on ILS and VOR approaches.

AIM Section 2. Performance−Based Navigation (PBN) and Area Navigation
  (RNAV)
1−2−3. Use of Suitable Area Navigation (RNAV) Systems on Conventional
  Procedures and Routes

Use of a suitable RNAV system as an Alternate Means of Navigation when a VOR, DME, VORTAC, VOR/DME, TACAN, NDB, or compass locator
  facility including locator outer marker and locator middle marker is
  operational and the respective aircraft is equipped with operational
  navigation equipment that is compatible with conventional navaids. For
  example, if equipped with a suitable RNAV system, a pilot may fly a
  procedure or route based on operational VOR using that RNAV system
  without monitoring the VOR.

NOTE−
  4. The navigation database should be current for the duration of the flight.
c. Uses of Suitable RNAV Systems. Subject to the operating
  requirements, operators may use a suitable RNAV system in the
  following ways.
    1. Determine aircraft position relative to, or distance from a VOR (“VOR” includes VOR, VOR/DME, and VORTAC facilities and “compass
  locator” includes locator outer marker and locator middle marker.),
  TACAN, NDB, compass locator, DME fix; or a named fix defined by a VOR
  radial, TACAN course, NDB bearing, or compass locator bearing
  intersecting a VOR or localizer course.

Navigate to or from a VOR, TACAN, NDB, or compass locator.
Hold over a VOR, TACAN, NDB, compass locator, or DME fix.
Fly an arc based upon DME.

None of the substitutions mentioned above include the localizer portion of an ILS. So you may not substitute GPS/WAAS for and ILS or localizer approach, but you may still use it for situational awareness.
You need to dig into the AIM to find out what they mean by “suitable RNAV system” but basically both certified GPS or WAAS count.

I believe a key factor in the "suitable RNAV system" is that the desired approach must be in the nav database for the system.  You can't manually enter approach fixes to create an approach.

@Gerry That’s true, the approach has to be in your database, but what they  say about "Suitable RNAV Systems’ is "the following systems qualify as a suitable RNAV system:

An RNAV system with TSO−C129/ −C145/−C146 equipment, installed in accordance with AC 20−138,… and  2. An RNAV system with DME/DME/IRU inputs that is compliant with the equipment provisions of AC 90−100A" For most people, that means certified GPS or WAAS systems.

Agreed, but I raised the point as it's entirely possible to have an approved "Suitable RNAV System" installed in your aircraft and not have the desired approach in your database.  I think it's an important factor when trying to determine "Can I fly a particular approach?"  Having an approved system won't help if the approach you want isn't in the database.

Reading at section in the AIM, the first note stipulates to read AC 90-108.  That AC says you cannot substitute a GPS/RNAV system on a Final approach segment. What does that mean?

AC No: 90-108 Change: 1 is Dated: 4/21/15. The AIM change is Effective: May 26, 2016. I’m guessing that the AC has not been updated yet OR there is another AC that the AIM is based on.

In reference to the OP’s original question about VOR and NDB procedures:
Yes for a Missed Approach Segment or Hold.
&
NO for a Final Approach Segment WITH LATERAL GUIDANCE.
The answer as it pertains to the final approach segment is NO if the Navaid is providing lateral guidance. And, you do not have to monitor the underlying Navaid EXCEPT for the final approach segment.
In other words, you can fly to, from, and around a Navaid without tuning in to the Navaid. You can even use GPS to fly to the runway while monitoring the Navaid. As soon as you are using Lateral guidance to align the plane with the runway for landing purposes, you have to use your Nav radio.
I imagine that the only time a VOR would provide lateral guidance by scaling would be if the VOR were located on the field. This is probably making a distinction between VOR/DME and NDB approaches not providing alignment guidance, and all other approaches. Probably since a VOR not located on the field will point you to the runway. But, it will not funnel or lead/guide you down to it (scaling).
And, your database must be current and contain the desired procedure to legally use the GPS.
See the below excerpt from the latest FAR/AIM as of 26 Jan 20. Specifically AIM 1-2-3 Notes section 2 & 4.
The FAR/AIM says:
Notes

The allowances described in this section apply even when a facility is identified as required on a procedure (for example, “Note ADF required”).
These operations do not include lateral navigation on localizer-based courses (including localizer back-course guidance) without reference to raw localizer data.
Unless otherwise specified, a suitable RNAV system cannot be used for navigation on procedures that are identified as not authorized (“NA”) without exception by a NOTAM. For example, an operator may not use a RNAV system to navigate on a procedure affected by an expired or unsatisfactory flight inspection, or a procedure that is based upon a recently decommissioned NAVAID.
Pilots may not substitute for the NAVAID (for example, a VOR or NDB) providing lateral guidance for the final approach segment. This restriction does not refer to instrument approach procedures with “or GPS” in the title when using GPS or WAAS. These allowances do not apply to procedures that are identified as not authorized (NA) without exception by a NOTAM, as other conditions may still exist and result in a procedure not being available. For example, these allowances do not apply to a procedure associated with an expired or unsatisfactory flight inspection, or is based upon a recently decommissioned NAVAID.
Use of a suitable RNAV system as a means to navigate on the final approach segment of an instrument approach procedure based on a VOR, TACAN or NDB signal, is allowable. The underlying NAVAID must be operational and the NAVAID monitored for final segment course alignment.
For the purpose of paragraph c, “VOR” includes VOR, VOR/DME, and VORTAC facilities and “compass locator” includes locator outer marker and locator middle marker.

d. Alternate Airport Considerations. For the purposes of flight planning, any required alternate airport must have an available instrument approach procedure that does not require the use of GPS. This restriction includes conducting a conventional approach at the alternate airport using a substitute means of navigation that is based upon the use of GPS. For example, these restrictions would apply when planning to use GPS equipment as a substitute means of navigation for an out-of-service VOR that supports an ILS missed approach procedure at an alternate airport. In this case, some other approach not reliant upon the use of GPS must be available. This restriction does not apply to RNAV systems using TSO-C145/-C146 WAAS equipment. For further WAAS guidance, see paragraph 1-1-18.

In #5 you quoted above it explicitly allows one to use a GPS to navigate on the final approach segment but the pilot must monitor the underlying navaid and follow that if the GPS and the navaid disagrees.

That’s the sticky wicket. Number 4 & 5 contradict each other. I think the key phrase is “lateral guidance”. Most of the examples of VOR and NDB IAPs don’t guide you down to the centerline of the runway using lateral scaling. You could be off as much as a mile and still have your CDI centered depending on how far away from the field the VOR is. On more than half the IAPs sampled, the final approach is either not even aligned with the runway and/or Circling only. I think that is the difference between the two sub-sections.

Something else that comes to mind is that the VOR IAPs sampled directed flight from the FAF as a Mag Course with no explicit mention of the Radial. Which is a point of irrelevant minutia since in all actuality, the Mag Course is the same or the reversal of the Radial. This might be interpreted as not explicitly getting the lateral guidance from the VOR. A more important point is that all of them have a waypoint as the MAP. So, technically the GPS is giving guidance to a waypoint and not lateral guidance for the approach runway. Thereby, falling under the rule of subsection 5.

Good info here, but I'd add a little interpretation and implied requirements as follows, as I don't see conflict between AIM 1-2-3(c) Notes 4 & 5 - though that is less than completely obvious.

AIM 1-2-3 (c) note 4: "lateral guidance" has nothing to do with runway alignment.  It is simply the left/right guidance provided by the NAVAID to follow a final approach course as depicted on the chart.  Runway alignment does not impact this note; the NAVAID must be referenced as provided in the note during the final approach segment, period.  So we are not allowed to simply fly a VOR or NDB approach using GPS needles and ignore the "raw" VHF data.  That's always been true.
AIM 1-2-3 (c) note 5: we can navigate with the GPS provided "the underlying NAVAID [is] operational and the NAVAID monitored for final segment course alignment."  So here's an example of a practical way of doing this: some AP systems can be flown in GPSS mode (navigating directly off the GPS) while the primary CDI still displays the VHF course information (i.e. the Avidyne PFD w/ separate GPS heads can do this; however, many systems, including G1000-based systems, cannot).  That gives a rock steady flight path (don't we love GPSS?) while showing the "raw" VOR data right on the HSI's CDI. Why do I think it should be a CDI type display (for VOR approaches) showing the "raw" data and not just the RMI style bearing pointer on your PFD pointing to the VOR?  Because pilots aren't expected to do math in their heads much and the requirements for "on course" (and "established") during the final approach segment are based largely on CDI deflection (3/4 max deflection for VHF approaches) and stability on the course and converting a bearing pointer to an off-course number of degrees or a rate of departure from a course (that is, a rate of lateral tracking error) and then knowing when too much is too much and time to go missed is much more difficult.  So without two CDIs available (and many do have that, but not all) then I think one has to go with the VOR indication on the one CDI.  Our local DPE's expect to see the VHF device on a CDI during an approach (FAF inbound), including VOR approaches - not just a bearing pointer.  So depending on your equipment you may or may not be able to actually fly the GPS and still monitor the VOR appropriately.
My $0.02; good thread, all.

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text:
What should a pilot do when flying in the vicinity of parachute jumpers?
There are several airfields nearby where parachuting activities routinely take place. How far away is considered to be a safe distance from the airfield when flying past it en-route to another destination? Are there any particular frequencies to monitor besides the airfield frequency? How would I know parachuting is happening besides any NOTAMs?

activity on the airfield and those big colored pieces of fabric coming down is a telltale sign :)

@ratchetfreak Activity on the airfield? Isn't any airfield going to have some sort of activity? And parachutes aren't as visible as you might think.

While in the Maryland Army National Guard, I accompanied a LURP Company to their drop zone (as a public affairs NCO to take pictures). They had contracted a private field (in WV) as a DZ. We were in the middle of their second drops of the day, when the field owner took off in an experimental light craft, right through the DZ. It was sheer luck that two troops came down to the left and right of him, instead of in front of... that was the scariest airport moment of my career. Afterward, the CO had a talk with the pilot, who said (basically) "my field, I take off when I want."

@CGCampbell: I'd love to know the legal repercussions on the owner if an incident had occurred.  In Sailing it is a fundamental principle that powered vessels are legally required to stay clear of non-powered vehicles, and motorized vessels must stay clear of non-motorized vessels. The only exceptions are for commercial vessels travelling at low speeds giving them no steerageway.

@PieterGeerkens I was with the command group during the discussions and it was decided that two jumps for the days was enough, mostly due to changing weather. No report was made (that I am aware) to any civil aviation authority, and the Captain decided it added more "real world uncertainties" to the drops. The troops cussed him (the owner) out and just got on to the days business.

If the field wasn't contracted as exclusive use only, it's good ol' see and avoid even during a jump...

Qualification: I worked at a busy drop zone for 10 years.
Just announce yourself on the airfield frequency about 5-10 minutes out and they'll tell you what's going on, including which runway is active and how high they are jumping from - standard altitudes are 3000ft and 12,000ft AGL. At our place it was really simple: left-hand for 34, right-hand for 16. We landed everyone on the east side, and if we are dropping at 3000 all day you can just pop up to 4000 and be completely out of the way.
Under no circumstances make a cross-field pass as that's usually right in the middle of everyone else's landing pattern, and we don't carry radios.
If you are just passing by a 2km buffer is lots - no one is likely to be in the air that far away.
No reply usually means nothing in the air.

What if the airfield is private and has no published frequency on the charts? That is the situation for one of the airfields nearby that are labeled as a parachute jump site. I happened to fly by it while on flight following and ATC notified me about parachuting, but if I hadn't been on flight following I wouldn't know. 2 km, I will use 2 miles, seems like a reasonable distance to remain clear. Thanks.

First of all, recurring DZ's have parachute symbols on sectional charts, so look for them!
The FAA regulations have this to say:
Federal Aviation Regulation Part 105.25 requires that ATC be notified no earlier than 24
hours before or no later than one hour before the parachute operation begins in Class E
and G airspace. Jumps in Class A, B, C and D airspace require an authorization from ATC.

This means that if you expect chute activity in the area, ask ATC!
Controllers are required to give traffic advisories to jump aircraft before the jump,
and to issue advisories to all known aircraft that will transit the Class E airspace
within which the jump operations will occur. When time or the number of aircraft make
individual transmissions impractical, advisories to nonparticipating aircraft may be
broadcast on appropriate frequencies.

And as always, check the NOTAMS!

That doesn't answer the question of how far. Will ATC provide separation? I assume it's not just a matter of see and avoid

I would say this is a judgement call. See and avoid is always a good fallback when unsure. Give them as much room as you think is safe, and them give them a little more.

The parachute symbols on sectionals can be unreliable.  If often takes years to get the symbol added. Once the parachute symbol is on the chart, it seems like they never go away.  The "Pig Farm" in southeast Wisconsin still has the symbol, even though there hasn't been jumping there since the 90s.

In Europe, it's generally a good idea to be on the Flight Information Service (FIS) frequency, where you can receive information about active drop zones and/traffic information to the airplane performing the drop, as they need to call in on the FIS frequency and announce when they start the drop.

Are there any particular frequencies to monitor besides the airfield
  frequency? How would I know parachuting is happening besides any
  NOTAMs?

Here in Seattle, jump aircraft are usually talking with ATC (Seattle Approach). The jump airplane will announce 5 minutes out and the when the jump occurs.

The 5 minute to jump contacting of ATC is required by law!

I'm not a pilot. I did attempt to get a parachute license, but stopped after a couple of jumps. I jumped at two different drop zones. (And I'm from Sweden) I just thought I'd offer a view from the other side.
At the DZs where I jumped, the pilot always talked to ATC before takeoff, so I would assume that ATC will know of any parachute activity.
The parachutists will fall, so if you can stay above the plane that will drop them, you'll be fine. Where I jumped, 4000 m was highest allowed altitude without oxygen, so no one jumped from higher than that.
The parachutists will want to land at or very close to their field. During the freefall part, they don't really drift with the wind. Chutes will typically be opened at about 1000 m, and from that altitude, they will drift significantly with the wind. Thus, they will be dropped upwind, and will typically not move very far downwind of the field, especially not at high altitudes.
So, in order of simplest/safest:

Fly above them
Fly downwind of their landing spot
If you need to fly close to their field, the higher up you can be, the better.

This should perhaps be taken with a few grains of salt, but hopefully others can chime in if I've said something incredibly stupid. :)

Welcome to Aviation.SE gibson. It's always good to have a view from a different perspective.

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text:
Safest deck on multi deck airplanes
It is a well known statistic that rear seats has higher survivability rates than front seats due to generally lower impact forces.
Double decks airplanes are not so common so statistics would probably be unreliable, especially since Boeing's only have a forward double deck.
Has any survivability study been made on that kind of aircraft, that include upper vs lower deck ?
I'm mostly interested in the a380 but other design are welcome as well.

Well, the JAL incident involved a 747 pretty sure, so you could probably assume a bit from that. Also, I would expect the same fundamental to be the same - the further forward you are, the less safe it would be.

I understand that, but I'm mostly interested into difference from upper and lower deck. Will edit the question to reflect that.

The only A380 to be involved in an accident was the uncontained engine failure on Qantas flight 32, which caused no injuries. Therefore, there are no survivability statistics for the plane.

Statistics for this are meaningless.  1.  Crashes are extremely rare.  2.  In most crashes where anyone dies, all die.  The differences between different seats become noise and rounding errors.  Any statistic will be that in the freak case where one passenger survived, they were sitting in 38C.  This says nothing useful.  The correct statement is that for all practical purposes, all seats are equally safe.

@Simon Your second point is incorrect: The majority of airline crashes that involve a fatality also involve one or more survivors.

Very difficult to say as we don't have enough real-world examples.
Vertical impact forces would be lower on the upper deck as the lower deck acts something like a crumple zone and absorbs some of the acceleration.
That said, an evacuation from the upper deck can result in more injuries due to the longer, steeper, slide that's needed.

Additionally, when acting as a crumple zone, the lower deck gets crumpled by the upper deck.


text:
Could the Shuttle Carrier Aircraft do a transatlantic flight with a Space Shuttle orbiter on its back?
Some of the STS backup landing sites were in Europe.
Of course, The STS would actually have to fly there only in case of extreme emergency, so the number one priority was just to save the lives of the crew members.
However, did NASA have a plan, or would it be doable to airlift the Space Shuttle atop an the Shuttle Carrier Aircraft like on this picture?

I'm especially curious about the range penalty induced by the additional drag of piggybacking the orbiter.
Picture credits: NASA / Carla Thomas, Public domain.

Consideration was given to in-air refueling and some preliminary test flights working towards it were done, but a concern arouse around turbulence and possible fatigue of the SCA tail so they stopped because there was no actual requirement for it.  The more interesting case is returning from pacific islands ;-)

Why not just fly the Shuttle across the Atlantic suborbitally.  Would have been interesting so see how much smaller the center fuel section was, and they would have beaten Virgin Galactic to it by 40 years, with more paseengers!

Short Answer
A procedure had been established to return from a Transoceanic Abort Landing (TAL) site to the Kennedy Space Center (KSC) using the Shuttle Carrier Aircraft (SCA). The maximum weight that could be ferried from Europe was approx. 87,000 kg, so so weight had to be removed from the orbiter prior to being mated.
The SCA had a maximum range, unmated, of 5,500 nautical miles, however when matted the range decreased to 1,000 nautical miles, using reserves. 4,500 NM were lost by carrying the orbiter. The SCA would have had to stop in UK, Iceland, Greenland, and Canada.
A test for in-flight refueling had been conducted but no solution was developed. From our friends at Space Exploration:

Studies were conducted to equip the SCA with aerial refueling
equipment, a modification already made to the U.S. Air Force E-4
(modified 747-200s) and 747 tanker transports for the IIAF. However,
during formation flying with a tanker aircraft to test refueling
approaches, minor cracks were spotted on the tailfin of N905NA. While
these were not likely to have been caused by the test flights, it was
felt that there was no sense taking unnecessary risks. Since there was
no urgent need to provide an aerial refueling capacity, the tests were
suspended.

A tailcone covering the 3 aft engines and the thrusters was used to reduce the drag and the buffeting on the SCA vertical stabilizers. It also protected the engine nozzles from being damaged in flight.
See below if you are interested by more details of the recovery plan.

Plan Used After Landing at the TAL Site
Operations to be conducted to return the orbiter to KSC were documented in a plan that couldn't be identified with certainty, however the US Department of Defense (DOD) plan to support the turnaround is quite descriptive of the operations. From DDMS TURNAROUND FUNCPLAN 3611-03 (C=TAL day):

The turnaround operation, to include redeployment of
personnel and equipment, may require up to 120 days to complete. [...]
C+18: JTF-DDMS staff coordinates with NASA for ferry flight route
support.
C+22: JTF-DDMS staff presents initial ferry flight support plan to NASA management.
C+26: NASA begins 24 hour turnaround operations to prepare and
mate the orbiter to the SCA for return ferry flight. [...]
C+53: Pathfinder and SCA arrive at landing site.

Slides explaining the DOD plan are also available.

TAL Site Operations
Each of the TAL site was equipped for the Orbiter landing and turnaround operations:

Navigation and landing aids
Weather equipment
Dedicated ground-support equipment
Emergency equipment
C-130 aircraft support

From Nasa Fact - Space Shuttle Transoceanic Abort Landing Sites:

Each TAL site is covered by a separate international agreement. The
TAL sites are referred to as augmented sites because they are equipped
with space shuttle-unique landing aids and are staffed with NASA,
contractor and Department of Defense personnel during a launch and
contingency landing.

Shuttle's Microwave Landing System (source)
In addition:

Safing and deservicing of the orbiter would be initiated by the
deployed TAL team and augmented by a team known as the Rapid Response
Team. [...]
The TAL site ground operations manager would initially be in charge
until relieved by a higher-ranking management official who would
arrive on the response/investigation team aircraft.
Within 24 hours, the response/investigation teams would arrive at the
TAL site aboard C-17 aircraft carrying personnel and equipment.  Most
of the equipment would come from Kennedy Space Center and Dryden
Flight Research Center in California.
Following the advance response/investigation teams contingent, the
Deployed Operations Team, consisting of additional personnel and
equipment, would begin arriving at the TAL site for the orbiter
turnaround operation. NASA estimates it would take about 19 C-17/C-5
aircraft sorties, a significant Navy sealift operation, and 450 NASA
and contractor personnel to complete the turnaround. [...]
Payloads and/or airborne support equipment will remain onboard the
orbiter for the flight back to Kennedy Space Center unless the
capability of the shuttle carrier aircraft, landing site location or
other requirements dictate other wise.

Lightening the Orbiter at the TAL Site Before Ferrying to KSC
Weight limits of the SCA:

Basic weight, NASA 905, 318,053 lbs (144,269 kg), NASA 911, 323,034 lbs (146,528 kg)
Maximum gross brake release weight, 710,000 lbs (322,056 kg)
Maximum gross landing weight, 600,000 lbs (272,160 kg).

From Space Transportation System Cargo Abort and Recovery Operations:

The ferry weight from contingency landing sites in Europe and Africa
is constrained to approx. 192,000 Ibs. (approx. 87,000 kg). The ferry
weight from the Pacific contingency landing sites is further
constrained to 154,000 Ibs. (approx. 70,000 kg).
This requires not
only removal of the payload but removal of Orbiter main engines,
tires, landing gear and other components as well. In addition, the
Orbiter Z axis (vertical) and X axis (longitudinal) center of gravity
location must be within a limited envelope, as shown in Figure 1.

From The Conquest of Space, Ferrying the Shuttle - Part Four: The Shuttle Carrier Aircraft:

A typical route might take the pair from
continental Europe to England, then on to Iceland, then Canada, and
finally to the United States.

(Additional information might be found in JSC-NSTS-08934-VOLUME-4, Space Shuttle Orbiter Ferry Plan.)

Mating and Demating the Orbiter
Photo gallery of Discovery mating at Edwards and demating at KSC (STS-114).

(Source: Nasa -- STS-114: Mission Complete)
The mating structure above couldn't be used at a TAL site, so a crane would be available for the operation:

Columbia being prepared at White Sands. Photo by Steve Schmidt.(Source: Abandoned and Little-Known Airfields)

Ferrying the Orbiter
From Nasa Fact, Shuttle Carrier Aircraft.
There were two SCA:

NASA 905: Obtained from American Airlines in 1974.
NASA 911: obtained from Japan Airlines in 1989.

They were B747-100 and B747-100SR, modified by Boeing into their SCA configuration.

(Source: Nasa Fact, Shuttle Carrier Aircraft)
They were engined by four Pratt and Whitney JT9D-7J, and had a fuel capacity of 316,307 lbs (143,477 kg).
The SCA didn't flight very fast: 250 kt or M .6, due to the drag from the orbiter and the additional vertical stabilizers. Its typical cruise altitude was also rather low to prevent freezing of the orbiter fluids:

with orbiter, 13,000-15,000 ft
unmated, 24,000-26,000 ft.

The range was hence a bit shorter than if it flew higher. Typical range:

Mated, typically 1000 NM (with reserves)
Unmated, maximum 5500 NM.

so they need 120 days and half of that is wasted on paper pushing. Typical government...

@jwenting: "120 days and half of that is wasted on paper pushing". The 200-300 persons mobilized before and after the Turnaroud main phase didn't do paperwork. See the linked detailed plan.

It's definitely worth having your ducks in a row before sticking the Space Shuttle on a 747 and flying it across the ocean.

@jwenting How long do you expect "a significant Navy sealift operation" to take?

Yes, it was possible and NASA had a plan. Enterprise was taken on a European tour in 1983, visiting the UK, France, Germany and Italy. To get there, it crossed the Atlantic on the back of the Shuttle Carrier Aircraft (the converted 747).  According to Slate, the range of the SCA was about 1,000 nautical miles so it made refuelling stops at Goose Bay and Keflavik on its way to London Stansted.

I hope the range of the SCA was closer to 1500 NM because Goose Bay to Keflavik is about 1300 NM.

@JamesKPolk That's an excellent point. Interestingly, the NASA document cited in mins' answer supports the 1,000nm range claim. It would be interesting if anyone can resolve this.

I would guess that the 1000 NM range is with a fully-loaded orbiter. The description in mins's answer suggests that, for a trans-Atlantic flight, the orbiter would be modified to reduce its weight.

Shuttle Enterprise doesn't have working engines. It probably weighs a lot less.

@KRyan mins' answer states a maximum of 87,000 kg for the SCA aircraft, which is odd because Wikipedia gives the empty weight of the Endeavour orbiter as 172,000 lb or 78,000 kg. The cited source states that the orbiter weight with main engines installed was 172,000 lbs, which works out to 78,018 kg. Maybe the problem was center of gravity more than sheer mass?

@aCVn http://www.astronautix.com/c/challenger.html lists the empty weight 79415kg with engines and that that's a metric ton less than Columbia. My guess is the removal of the engines is more to reduce the weight to allow for the range required rather than to allow the orbiter to be lifted at all.

@JamesKPolk: There are airports in Greenland; if they'd had to ferry an actual flightworthy orbiter, they probably would have stopped at one of those.

Apparently Yes.
From NASA document Space Shuttle Transoceanic
Abort Landing (TAL) Sites(emphasis mine):

Payloads and/or airborne support equipment will remain onboard the orbiter for the flight back to Kennedy Space Center unless the capability of the shuttle carrier aircraft, landing site location or other requirements dictate otherwise.

The document also details the procedure to be followed in case the TAL is to be used. TAL sites were 'activated' prior to launch and a C-130 was kept on standby for evacuation and emergencies.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
Rolling take off compared to take off from a standstill
When ever I fly I choose flights with the most take off and landings. After going down the taxiway and turning onto the runway sometimes the flight crew ramp up the engines up while holding the airplane from moving with the brakes, then let off the brakes and the plane shoots down the runway like a rocket sled on on wheels. Other times the plane will go down the taxiway, turn onto the runway and without stopping ramp up the engines and head down the runway. What is the difference in these two techniques? Is it pilot choice?

Boeing recommends a rolling takeoff for setting takeoff thrust. It
expedites takeoff and reduces the risk of foreign object damage or
engine surge/stall due to a crosswind. The change in takeoff roll
due to the rolling takeoff procedure is NEGLIGIBLE when compared to
a standing takeoff.

There are a few things that may be going on.
Generally the foot on the breaks, full throttle, spool up, release and roll is derivative of a short field takeoff. In other words you need all available runway and all available power to get off the ground safely and clear your runway end obstacles. This is dictated by airplane performance and runway conditions/length.
Roll on, roll into full throttle and go is more or less standard. In some cases this may follow an ATC clearance like

123AB Cleared for takeoff 22 depart no delay

This generally means there is either someone inbound for a landing but theres time for you to go, or there is a long queue on the ground and the controller wants you to get going. Stopping on the runway to spool up your engines takes time and at a busy field that can be in short supply.
Its important to note that in any case the pilot should line the aircraft up with centerline prior to applying full throttle.
The aircraft can also be instructed to, "line up and wait" in which case its cleared to enter the runway and wait on the numbers until cleared. This may occur at an airport that offers parallel runway operations and the aircraft is waiting for a plane to land on a parallel runway.

EDIT: I found a possible dupe, noted in the comments. Its a bit different so ill leave this answer here and let the community decide.

Depends on the takeoff procedure being employed as well as the aircraft type.  Rolling takeoffs are a preferred procedure for soft field takeoffs on grass strips which may have high grass or wet sod and the aircraft is kept rolling to prevent the possibility of the landing gear becoming stuck in the muck.  Short field takeoffs involve lining the aircraft up on centerline as close to the threshold edge as possible, applying brake pressure while running the engines to full power, thence releasing the brakes and commence the takeoff roll.  This is done to miminimze the amount of runway needed to perform the takeoff roll on.  Multi engine airplanes will use the same technique in order to conform with manufacturer performance data on accelerate-stop and accelerate-go distances, which are a necessary performance metric to have established as part of the pre-takeoff brief for emergency contingencies in the event of an engine failure.  This is the standard takeoff procedure when flying multi engine aircraft.
In the case of most airliners and civil jets in general, they will usually hold brakes and establish 60% or so of the selected takeoff thrust in order to accomplish a final check on the engines, then release brakes and increase to takeoff thrust.  A pilot may opt to hold brakes and throttle to takeoff thrust first then begin the takeoff roll.  As for rolling takeoffs, one could argue it’s sloppy airmanship but plenty of fleet pilots do it on a regular basis.

before takeoff, the pilot knows the handbook values for balanced runway length for any density altitude, the gross weight of the plane, and the runway length available. If there is far more runway length available than the handbook requires, then upon being cleared the pilot may elect to roll on, start the run, and go to full power. If not, the pilot should instead roll into position, stand on the brakes, spool up the engines, check gauges for full power, release brakes and roll.
Of course, ATC has the final say, and as pointed out by Dave, may specifically instruct the pilot to do one thing or the other depending on what's required.


text:
What is the best distance glider that can carry a 200 lb load?
Good morning, I'm an emigrant from Worldbuilding and I ask this first question in part to help me discover what I don't know I don't know.
My definition of best: Longest recorded single flight time with closest to maximum load. I might be misusing some terms, but I'd prefer design that itself was 100lbs or less and could still carry 200 additional lbs (90kg).
I think I used appropriate tags but feel free to provide suggestions and requests for more information.

You're asking "how far can a glider that weighs less than 100 lbs and can carry 200 lbs fly"?

Launched from what height? What kind of atmospheric conditions? Are there mountains or other terrain nearby to take advantages of updrafts? Localized weather? There are too many variables to say that a glider weighing X can go Y distance, gliders don't just descend, you can climb in a glider too, to over 50,000 feet.

@DanPichelman Sorta. I want to see what the glider that can fly the farthest with 200 lbs looks like and how it is built.

@RonBeyer My definition of best includes 'longest recorded single flight'. So the longest flight that actually happened and was recorded by a glider that was less than 100 lbs. That would probably require the ideal situation.

It would very much depend on weather conditions (updrafts) and pilot skill.

Kind of like this: https://en.wikipedia.org/wiki/Hang_gliding  There are 2-place hang gliders, so that meets your 200 additional pounds criterion.

best glide slope donnot depend on the weight (but the speed at which you can glide near to this best glide slope do depend on weight).

Google "tandem hang glider" and "tandem hang glider record distance".  Not sure whether any one actually keeps distance records for tandem hang gliding flights or not.  However  the truth is that many long distance hang gliding flights have been set with a payload of over 200 pounds if you consider combined weight of pilot, harness, parachute, helmet, instruments-- this stuff probably almost always adds up to more than 30-40 pounds over pilot body weight.

Hang gliders weigh less than 100lbs and some can carry 200lbs.
The FAI distance record is 475 miles and must have taken hours to accomplish.  Note that the distance is measured as a point-to-point distance, not as actual ground track distance.  Unpowered airplanes require lift to stay aloft and must circle in rising colums of air to gain altitude.  The 475 mile record may have required a significantly larger number of ground track miles to achieve.
There are generally two ways to gain altitude:
First, find a rising column of air (thermal).  This is as simple as flying in a straight line until you feel a wing rise (indicating lift).  Turn INto the lift and continue to circle until you stop climbing.  Youtube has many examples of this.
Second, ascend into a lee wave.  A decent wave will get you >30,000' from which you can set out in search of thermals or more waves.  Bring oxygen.
Both of these require the glider to be towed aloft or launched from a higher elevation (ex. a mountain).

This answer would be improved by adding a section about ridge soaring, and deleting or modifying the section about lee waves.  Hang gliders almost never fly in lee waves because the wind and potential turbulence is typically just too strong for them.  Also each individual sentence or paragraph is a little unclear as to whether you are referring to hang gliders, sailplanes, or both.  This answer could be greatly improved with just a little work.

To improve performance over that of conventional hang gliders, you need a rigid wing. Here is a directory of light sport aircraft; there are quite a few which weigh 100 lbs empty or less. My recommendation would be the Swift lite, a development of the Swift foot launched glider. Yes, at 48 kg it busts your limit of 100 lbs, but not by much.

Swift foot launched hang glider in flight (picture source)
Here is a more detailed description. The Swift is so much better than conventional hang gliders that it has been banished from competitions and placed in a separate class. A two-seater version has also been developed; this should be capable of carrying a 200 lbs payload in addition to the pilot.


text:
Why does X-Plane 11 show the SR-71 at 200 knots but Mach 3 at 80,000 ft?
So I noticed on X-Plane 11, the SR-71 reaches Mach 3 at 80000 feet, but the equivalent airspeed is only around 200 knots. What explains this difference between the mach number readout and the EAS readout?
Edit: the reason I ask is because other questions such as How did SR-71 spy, flying at 80,000 ft and 3500 km/h? indicate the SR-71 flew at 1910+ knots at 80000 feet, but I'm not sure if this is with a conversion of some sort or not, i.e., is this simply a simulator problem or an accurate representation of airspeed and mach?

related: https://aviation.stackexchange.com/q/3693/1467

You can use this calculator. Under standard atmosphere, at 80,000 ft the speed of sound is 579 kt (661 at sea level), but density is only 0.043 kg/m3 (1.23 at sea level). That explains why the indicated airspeed is very low.

I've worked out an answer to this. I get indicated airspeed = 401 m/s = 780 kts. I cannot post the answer because while I was composing it, using this equation, the question was closed. The cited questions for duplicate do not list a direct answer to this question. Requesting that this question be re-opened please, so I can post the answer.

Thx for re-opening. Equation above is for incompressible flow only, got a value in order of magnitude of X-plane.

Maybe you should call for a ground speed check... you'd get an accurate answer, and it would quiet down any fighter jocks nearby.

If you ever do the math and find the simulator to not be accurate you can always file a bug.

Indicated airspeed is derived from the measured total pressure and the static pressure, according to:
$$ V_i = \sqrt {\frac{2 \cdot (p_t - p_s)}{\rho_{SL}}} \tag{1}$$
At 80,000 feet, static pressure is 2761 Pa. Dynamic pressure as measured by a pitot tube, is measured after a supersonic shock wave according to the Rayleigh Pitot tube formula:
$$ \frac{p_t}{p_s} = \left[\frac{{(\gamma + 1)}^2 \cdot M^2}{4\cdot\gamma \cdot M^2 - 2(\gamma - 1)} \right]^{\gamma / (\gamma - 1)} \cdot \frac{1 - \gamma + 2\cdot \gamma \cdot M^2}{\gamma + 1} \tag{2}$$
with $\gamma = 1.4$ and M = 3, substituted in (2), gives $\frac{p_t}{p_s} $ = 12.06, so $$p_t = 12.06 * 2761 = 33\,290 ~\text{Pa}$$. Substitute this into (1) together with $\rho$ = 1.225 at sea level, and we get
$$ V_i = \sqrt{\frac{2 \cdot (33,290 - 2761)}{1.225}} = 158 ~\text{m/s} = 307 ~\text{kts}$$
In the order of magnitude of what the X-plane indicated airspeed indicates, a lot closer than the TAS: speed of sound @ 80,000 ft = 298 m/s, Mach 3 = 894 m/s = 1,738 kts

Very cool – so if I follow, the short answer is yes, the readouts on X-Plane are more or less accurate for Mach 3 at 80,000 ft, being much lower than the TAS. Incidentally, since the Blackbird seems to measure EAS instead of IAS, I should have earlier referenced Equivalent airspeed, which makes for a much easier calculation, essentially multiplying the TAS by about 5 to get the EAS at 80,000 ft. So the numbers on the simulator all seem to check out.

Is 307 kts for EAS or IAS?

The 307 would be for IAS.

I already knew the speed of sound decreases with increasing altitude – I was actually trying to figure out why the Blackbird Wikipedia specs list a speed of 1910+ knots at 80,000 ft when the EAS only read 200-300 knots at said altitude. The conversion between EAS and TAS explains the difference.
It turns out I made a simple problem out to be harder than it was. Since the Mach numbers of the Blackbird are non-trivial, EAS is used instead of IAS, and per Equivalent airspeed, using
EAS = TAS * sqrt(p/p0)
with p being the actual air density at 80,000 ft of .043 kg/m^3 and p0 being the standard sea level density of 1.223 kg/m^3, making the EAS roughly a fifth of the TAS. So a TAS of Mach 3, 1,738 knots, would have an EAS of 326 knots. I assume, then, the simulator is more or less accurate.

Equivalent Air Speed at Mach 3 is not that simple to convert. The equation you're using is valid for subsonic flows that may be considered incompressible and for which we can take dynamic pressure $ p_d = \frac{1}{2} \rho V^2$

Are any of the equations listed on the Wikipedia page usable then?

It's a bit of a hard one. There are lots of references to the EAS for incompressible, subsonic flow, not so many for high supersonic flow. When I look it up in this Flight Testing manual eq. 4.28 I get a much higher value.

Referring to a much higher value for the EAS for Mach 3 at 80,000 ft?

Yes indeed. In trying to get to the bottom of it I got stuck in trying to figure something out on supersonic dynamic pressure

All this calculated stuff is impressive. I just figure the air density at 80.000 is less dense and it doesn't have enough pressure to force the airspeed indicate  up. Being it takes air pressure in the pet tube to cause the airspeed indicator gauge to go up in numbers. Even though it's only shows 200 knots, it's speed over the ground is much faster.
So I'm thinking it could be close to stalling if it go's any higher unless it can push it's self faster. If I remember corect the 71 rotation speed is 180 knots.
This is a interesting subject. I know the space shuttle shows no airspeed until it inters the atmosphere. I wounder what the numbers are on it.

You are describing indicated air speed. you can improve your answer by putting this term in it.


text:
Feasibility of converting long body carriers into stationary field hospitals
Considering the current pandemic crisis, and the fact that and there are thousands of grounded planes that can be put to other uses, I come with a somewhat dumb question.
Is it possible to remove seats in a long-body passenger carrier to, instead of flying with two hundred cramped passengers, make it spacely enough to carry forty or fifty narrow beds and a small staff to take care of them, while stationary on the ground?
Is it feasible, from an economic viewpoint, to pay air companies for this, in comparison to actually building tents or renting buildings in a big town like New York or San Francisco?
EDIT
Yeah, I mean stationary planes, with external APU to power up the air conditioning and lights and rampies to take the waste away and constantly fill it with water.

Probably simpler and no reason not to work is to convert the airport passenger area into hospital.

Actually, train cars and ships are more suitable for these kind of tasks and has been done. Grounding an airplane is kind of expensive, compared with trains and ships.

I like your invention of the new word "spacely"

Better  to use military ships as they are all infected anyway or soon will be, and they are bigger than airliners.

Hotels, convention centers, schools, and other buildings would be far better choice.  No special benefits from using airplanes, and I could see a lot of downsides...

There's no way you're going to fit 50 beds, dividers, and all the equipment required in a jet, then power it all on top of that.

short answer: yes it is feasible as it is done for medical evacuation but not needed as other transformations are cheaper and more effective (more space, easier to get in and out of a building than a plane, ...)

This is a very opinion based question that will garner many opinion based answers. Not the type of type of fact based question that is the purpose of this site.
The pros of this concept would be:

Provide revenue for the airline.
Provide space for the ill.

The cons of this concept would be:

Aircraft get awfully hot or cold when not being powered.
There are no adequate facilities for long term waste and hygiene.
The air in an unpowered aircraft would be awfully stagnant. That is not good for the health of the recovering, nor that of the medical personnel.
If worse came to worse, there are a lot of unoccupied buildings that can be rented at the same or less cost than an airplane. They would already have the infrastructure for power and plumbing.
The Army and Army National Guard already have most of the tents and other housing facilities bought, paid for, and in storage for these types of emergencies.
Even for a pilot, timeframe for recovery, stuck in a fuselage, with that many other people would be claustrophobic. Think of how it feels if you are under a stay-at-home sequester order, now. Now, multiply that by ten.
Costly decontamination post-pandemic.
Running an engine or APU 24/7 would be cost prohibitive.
Having lived in a space with fifty other guys for an extended period of time, even with bunk beds, I can tell you that it would require more space than you might think. 1000 square feet (100 m^2) would be my estimate of the bare minimum without dining nor food preparation facilities, and minimal toileting facilities. That would be 20 square feet per person. That is less space than a king sized bed per couple for the entire living space.
Cruise ships and hotels would be a more feasible option.

I like cruise ships and hotel options, using planes like that can be reduced to a very peculiar situation, if any.


text:
Is it possible to take PPL lessons in different locations and countries?
I have been wondering if it is possible to do flight lessons in different locations? For example, I am currently taking my PPL lessons (VRF) in Manchester, UK. I usually travel between countries in Europe and America.
I was wondering if my travels take longer than 2 weeks if it was also possible to take the opportunity to do a lesson in one of them? Or if regulations would made it impossible to do so?

You might be able to book some one-off lessons in the USA that don't count toward your EASA PPL.  You might have TSA issues though.  Also, I've found that instructors can have very different views of things and there might be inconsistencies (quite apart from different procedures, radio rules etc.)

As a practical matter, it will probably be too much hassle to get signed up with new flight schools in each city/country you visit for only one or two lessons, especially in the US where you need certain classes of visa (no VWP), permission from DHS, etc.
Also, FAA and ICAO/EASA rules can be pretty different. If you know one well, you can fairly easily learn the other (or just muddle along without anyone noticing), but I wouldn't want to mix the two during primary training. Learning one set of rules is hard enough.
The only case where this might make sense is if you'll be visiting the same city repeatedly and can get the same instructor every time, which eliminates most of the overhead. I did this (both cities in US), and my home instructor would give me a specific list of things to work on for each trip, and when I came back, I'd show what I'd learned and we'd move on to the next thing. After I soloed at home, I did a mock checkride for my other instructor and he soloed me too. Having two instructors did cost me more in total flight time, but it minimized calendar time because instead of losing proficiency by having long gaps between lessons, I was gaining proficiency by flying regularly. It also helped that the two had different teaching styles, so if one wasn't getting through to me, the other would. Still, I wouldn't recommend it if there's any other option

is always refreshing to read the so many different stories/experiences people have! Thank you for sharing this ^^

This is an answer based on experience, if someone knows corresponding regulations or if I’m writing something not 100% correct, feel free to edit it.
First of all: It’s possible to switch flight schools between countries (what I did).
But regarding doing it while traveling: it depends on which countries and the flight schools. In Germany for example you have to be registered at the authorities in order to get flight lessons and that’s as far as I know exclusive (it’s only possible if you’re not registered somewhere else) but I might be wrong there. I’m not aware of any EASA regulations that prevent it.
The most practical answer for you is probably to check with both your flight schools and those at your travel destinations, if they think, something is possible.
Edit: this just applies to other EASA countries. I don’t think you will have chances outside EASA countries except for if you have ATOs there that are approved as EASA-ATOs.

Thank you @Florian, for sharing this! :)


text:
What does the practical CPL skill test contain?
In EASA Part-FCL, FCL.310 containts on several hundred pages all the required knowledge for the theoretical skill test for a CPL. However, different from other licenses described in Part-FCL (PPL, Aerobatic, VFR Night, Mountain, ...), there is no list of what's in the practical skill test.
What's included in the CPL practical skill test? What are the tolerances for maneuvers etc?

The section of the document on the CPL skills test says that the test requirements are in Appendix 4. Is the information in Appendix 4 what you need?

https://www.easa.europa.eu/sites/default/files/dfu/Part-FCL.pdf

Appendix 4 - Skill test for the issue of a CPL
A. General
  1. An applicant for a skill test for the CPL shall have received instruction on the same class or type of aircraft to be used in the
  test.
  2. An applicant shall pass all the relevant sections of the skill test. If any item in a section is failed, that section is failed.
  Failure in more than one section will require the applicant to take
  the entire test again. An applicant failing only in one section shall
  only repeat the failed section. Failure in any section of the retest,
  including those sections that have been passed on a previous attempt,
  will require the applicant to take the entire test again. All relevant
  sections of the skill test shall be completed within 6 months. Failure
  to achieve a pass in all relevant sections of the test in two attempts
  will require further training.
  3. Further training may be required following any failed skill test. There is no limit to the number of skill tests that may be attempted.
CONDUCT OF THE TEST
  4. Should the applicant choose to terminate a skill test for reasons considered inadequate by the Flight Examiner (FE), the applicant shall
  retake the entire skill test. If the test is terminated for reasons
  considered adequate by the FE, only those sections not completed shall
  be tested in a further flight.
  5. At the discretion of the FE, any manoeuvre or procedure of the test may be repeated once by the applicant. The FE may stop the test at any
  stage if it is considered that the applicant’s demonstration of flying
  skills requires a complete re-test.
  6. An applicant shall be required to fly the aircraft from a position where the PIC functions can be performed and to carry out the test as
  if no other crew member is present. Responsibility for the flight
  shall be allocated in accordance with national regulations.
  7. An applicant shall indicate to the FE the checks and duties carried out, including the identification of radio facilities. Checks shall be
  completed in accordance with the checklist for the aircraft on which
  the test is being taken. During pre-flight preparation for the test,
  the applicant is required to determine power settings and speeds.
  Performance data for take-off, approach and landing shall be
  calculated by the applicant in compliance with the operations manual
  or flight manual for the aircraft used.
  8. The FE shall take no part in the operation of the aircraft except where intervention is necessary in the interests of safety or to avoid
  unacceptable delay to other traffic. B. Content of the skill test for
  the issue of a CPL — Aeroplanes

The aeroplane used for the skill test shall meet the requirements for training aeroplanes, and shall be certificated for the carriage of
  at least four persons, have a variable pitch propeller and retractable
  landing gear.
The route to be flown shall be chosen by the FE and the destination shall be a controlled aerodrome. The applicant shall be responsible
  for the flight planning and shall ensure that all equipment and
  documentation for the execution of the flight are on board. The
  duration of the flight shall be at least 90 minutes.
The applicant shall demonstrate the ability to: (a) operate the aeroplane within its limitations, (b) complete all manoeuvres with
  smoothness and accuracy, (c) exercise good judgement and airmanship;
  (d) apply aeronautical knowledge; and (e) maintain control of the
  aeroplane at all times in such a manner that the successful outcome of
  a procedure or manoeuvre is never seriously in doubt.

FLIGHT TEST TOLERANCES
  4. The following limits shall apply, corrected to make allowance for turbulent conditions and the handling qualities and performance of the
  aeroplane used. Height normal flight ±100 feet with simulated engine
  failure ±150 feet Tracking on radio aids ±5° Heading normal flight
  ±10° with simulated engine failure ±15° Speed take-off and approach ±5
  knots all other flight regimes ±10 knots
CONTENT OF THE TEST
  5. Items in section 2 (c) and (e)(iv), and the whole of sections 5 and 6 may be performed in an FNPT II or an FFS. Use of the aeroplane
  checklists, airmanship, control of the aeroplane by external visual
  reference, anti-icing/de-icing procedures and principles of threat and
  error management apply in all sections.
SECTION 1 — PRE-FLIGHT OPERATIONS AND DEPARTURE a Pre-flight,
  including: Flight planning, Documentation, Mass and balance
  determination, Weather brief, NOTAMS b Aeroplane inspection and
  servicing c Taxiing and take-off Part-FCL – Appendices, AMC and GM V1,
  June 2016 Go back to Appendices Go back to the content 1168 | P a g e
  d Performance considerations and trim e Aerodrome and traffic pattern
  operations f Departure procedure, altimeter setting, collision
  avoidance (lookout) g ATC liaison – compliance, R/T procedures
SECTION 2 GENERAL AIRWORK a Control of the aeroplane by external
  visual reference, including straight and level, climb, descent,
  lookout b Flight at critically low airspeeds including recognition of
  and recovery from incipient and full stalls c Turns, including turns
  in landing configuration. Steep turns 45° d Flight at critically high
  airspeeds, including recognition of and recovery from spiral dives
  eFlight by reference solely to instruments, including: (i) level
  flight, cruise configuration, control of heading, altitude and
  airspeed (ii) climbing and descending turns with 10°–30° bank (iii)
  recoveries from unusual attitudes (iv) limited panel instruments f ATC
  liaison – compliance, R/T procedures
SECTION 3 — EN-ROUTE PROCEDURES a Control of aeroplane by external
  visual reference, including cruise configuration Range/Endurance
  considerations b Orientation, map reading c Altitude, speed, heading
  control, lookout d Altimeter setting. ATC liaison – compliance, R/T
  procedures eMonitoring of flight progress, flight log, fuel usage,
  assessment of track error and re-establishment of correct tracking f
  Observation of weather conditions, assessment of trends, diversion
  planning g Tracking, positioning (NDB or VOR), identification of
  facilities (instrument flight). Implementation of diversion plan to
  alternate aerodrome (visual flight)
SECTION 4 — APPROACH AND LANDING PROCEDURES a Arrival procedures,
  altimeter setting, checks, lookout b ATC liaison - compliance, R/T
  procedures c Go-around action from low height d Normal landing,
  crosswind landing (if suitable conditions) e Short field landing f
  Approach and landing with idle power (single-engine only) g Landing
  without use of flaps h Post flight actions
SECTION 5 — ABNORMAL AND EMERGENCY PROCEDURES This section may be
  combined with sections 1 through 4 a Simulated engine failure after
  take-off (at a safe altitude), fire drill b Equipment malfunctions
  including alternative landing gear extension, electrical and brake
  failure c Forced landing (simulated) d ATC liaison - compliance, R/T
  procedures e Oral questions
SECTION 6 — SIMULATED ASYMMETRIC FLIGHT AND RELEVANT CLASS OR TYPE
  ITEMS This section may be combined with sections 1 through 5 a
  Simulated engine failure during take-off (at a safe altitude unless
  carried out in an FFS) b Asymmetric approach and go-around c
  Asymmetric approach and full stop landing d Engine shutdown and
  restart e ATC liaison – compliance, R/T procedures, Airmanship f As
  determined by the FE — any relevant items of the class or type rating
  skill test to include, if applicable: (i) aeroplane systems including
  handling of autopilot (ii) operation of pressurisation system (iii)
  use of de-icing and anti-icing system g Oral questions

Please use block-quotes if you are quoting a body of text that you did not write/author. You should also link to the original source document and cite the page/section/etc where you found the information, otherwise this is just a copy/paste answer with no attribution.

Got it.      Thanks.


text:
What’s this vortex generator like thing below the wing?
In Barcelona’s El Prat Airport I saw some ceiling fans and noticed that they have on the lower part of the wings something that looks like a wingtip device or vortex generator.
As far as I understand vortex generators, they prevent the boundary later to detach / move the separation point. But that’s no issue below an airfoil, is it?

Can it be related to protection against sharp edges for maintenance people?

They are seldom maintained or paid any heed to. The last couple of times I had a connection through BCN or VLC (which has the same fans), some of them were turning in the wrong direction (trailing edge into the flow)...

The manufacturer, Big Ass Fans, calls those devices “air fences.” Based on this naming I assume they are most likely there to redirect spanwise flow on the longer airfoils, not to prevent separation. Such a narrow airfoil built to move at a steady speed and loading would probably not suffer from separation issues. They are basically the same as wing fences.

source:Big Ass Fans website
Wing fences are usually found on swept wings, because that’s what’s responsible for the spanwise flow, and the fan blades don’t appear to be swept. But in the case of a fan there will probably be a certain amount of radial flow due to the spinning motion. After a significant distance this could build up to be significant enough that the fence might help to redirect it.

What a name for a company. Thanks!

Hilarious, isn’t it. If you zoom in it’s written right on the fan in your pic

Since this fan uses 8 blades a blade will experience significant wake turbulence from the blade in front of it.  Due to the rotational nature of the fan the wake turbulence will have a span wise component.  The wing fences will limit this.  The "winglets" are meant to reduce the vortices at the tip to also mitigate the wake turbulence problem.  This kind of ties in to why we don't just add blades to a propeller to get more thrust.  You don't normally see this much engineering in a ceiling fan.


text:
How do airlines and airport exchange data?
I was just waiting for a flight, when the airline’s app sent me a push notification; my gate was changed to 12 in the same moment that the airport notified passengers about that the gate was changed to 15. So I started wondering how airlines and airports exchange this information?
Is it a central IT system? Run e.g. by IATA? Or do the alliances (star alliance etc) have central systems for that and they connect to airports? Or are there individual contracts between airlines and airports they go to? Does everyone use the same protocol / standard? Or is it more chaotically?
Additionally, flightradar24 recently started including gate & baggage belt information in their service – do they get it (likely) from the airports? Or do the airlines provide that data? Or how does that work?

Most of the information regarding airport operations are handled by the airport (gate, baggage belt, aircraft location etc.), stored in their database and provided via an API to operators (airlines) and the general public. Regarding Flightradar24 they have a page explaining how they collect and manage data

@PierreChevallier How is that not an answer?

I didn't have much more information, but I'll write a more complete answer.

Introduction : determining which gate is assigned
I assume we are talking about IFR flights with the purpose of passenger travel.
An aircraft, in order to be assigned to a gate, has to be planned and to arrive at an airport.
So let's look at the breakdown of arrival of an aircraft.
First, the airline (operator) has filled a flight plan before the flight occurred and submitted it to the legal authority managing flights in the airspace (Aeronautical Navigation Services -ANS- typically) in order to have clearance to enter the airspace, getting navigation informations and accessing the airport (more on this matter). At this moment, the airport gets informations about the next aircrafts (operator, type of aircraft, passenger, cargo etc.), which will be managed upon arrival.
Secondly, after being handled by Area Control Center (ACC) ATCO (en route flight), the aircraft is routed towards the airport by Approach controllers (APP) which manage the airplane when it flies from en route (high altitude) to the airport (ground); when the aircraft is lined up with the runway a few miles from the airport it is transfered to the tower which manages the operations from this moment (given no go around has been initiated due to runway incursion, landing mishaps etc.) and will most importantly manage ground operations (taxiing, handling take-off and landing sequences etc.).
Once the aircraft has landed and starts taxiing, the tower (TWR) will give directions to the gate it would be assigned, depending on various factors:

Negotiations with the operator : location of the aircraft at the airport has a price, aprons are more costly than parking the aircraft further from the terminal and being handled by a bus for example.
Destination and origin of the aircraft : international and regional flight can be handled in different terminals: e.g. in Europe, Schengen area flights are usually handled separately from outside the Schengen area.
Size of the aircraft : for example A380 are notable for being difficult to maneuver around airports and need specific aprons and some airport have only a few gate that can be assigned to such specific aircraft.
Available spots : the airports are incredibly busy around noon every day (look at the traffic at a major airport like Heathrow around that time), which means that some spots might be taken and the airport has to accommodate the aircraft at an available gate.

Information exchange
The tower exchange directly with the aircraft (crew or the aircraft itself) via radio or data-link, they give directions and update the gate according to the current available spots. It seems (so I might need more information with somebody more familiar with the matter) that data-link is use in most cases to share informations regarding flight details between ground and aircraft.
All in all, the airport tower decide and manages the gate. The information are stored in an operational database (at the tower or the ANS provider) and are provided to aircrafts, operators and passenger (terminals and online).
Generally speaking, the data is provided to operators via the database and a technical overlay, this can vary depending on the regions. In Europe, operators  rely on Eurocontrol Network Manager Operations Centre to exchange informations regarding flight plans, updates of flight plans and different informations regarding operations. I don't have information regarding other regions like North America.
Airport-Collaborative Decision Making
A big topic at the moment for the European airports is the principle of Airport Collaborative Decision Making (ACDM for short) which should improve the quality and reliability of these informations, by sharing information directly from the airport and the NMOC of Eurocontrol.
Though this topic is to large to cover here, it would improve such information being shared between operators, airports, aircrafts etc. and normalise the way information is shared.
Flightradar24
As for Flightradar as I pointed out in the comments, they have an explanation of how they work with data.

A final word, it seems that airport API are usually not public, and it can be expected that for examples airlines do not have other's flight information (and gate per se).


text:
Is the "PROB" in a TAF only applying to the next group or all following ones?
Let's assume I have a TAF that reads:
[...]
PROB40
TEMPO 0815/0822 5000 -SHSN BKN008 OVC015
TEMPO 0822/0909 1000 SN VV003
BECMG 0902/0904 16012KT

Which of the TEMPO / BECMG groups have a probability of 40%? All three because everything that follows PROB40 has a probability of 40%? Just the first TEMPO because PROB40 only means the one following line in the TAF? Or both TEMPO ones, and BECMG is again certain and not just 40% probable?

PROB40 is targeted only on the immediate TEMPO group. If there are several PROB/TEMPOs both keywords must be repeated every time. Also, PROB is never associated with BECMG or FM groups, which indicate permanent change.

Welcome to Av.SE -- nice answer.


text:
Carburetor Heat Required on Carburetor equipped GA aircraft?
Is Carburetor Heat Required (by FAA Certification regulations) on Carburetor equipped GA aircraft?
If not, what (if any) certified carburetor-equipped GA aircraft do NOT have Carburetor Heat installed ?

Carb heat is not specifically required by regulation. What is required by the following rule is a means to prevent ice accretion:

14 CFR 33.35 Fuel and induction system.
(b) The intake passages of the engine through which air or fuel in
  combination with air passes for combustion purposes must be designed
  and constructed to minimize the danger of ice accretion in those
  passages. The engine must be designed and constructed to permit the
  use of a means for ice prevention.

Carb heat is the most common solution, but alternate solutions may be acceptable.


text:
Why do F16's have anhedral tail wings?
I just wonder why F16's have anhedral tail wings?

Is it kind of a design choice to increase maneuverability by compromising stability?

All recent US jet fighters have been designed as inherently unstable to increase performance.

The purpose of the anhedral is to get the tail surfaces away from the wing wake. The distance between the wing's trailing edge and the horizontal tail is low enough so that the tail needs a vertical offset in order to have full dynamic pressure available locally.
Earlier designs moved the tail up for the same reason (Lockheed F-104, Grumman F-9F) until it became obvious that at some angle of attack some airplanes could get into a deep stall. Especially with the wider angle of attack range possible with swept, low aspect ratio wings no position above the wing's plane is safe anymore.
For that reason all modern fighter aircraft position the horizontal tail as low as practical. This in turn has led to situations where ground effect is so strong that other tricks had to be employed to get the airplane to perform as intended.
Stability is not affected, aside from a small positive contribution to the sideslip-induced rolling moment. This is easily compensated by adjusting wing dihedral properly. Or, in other words, the F-16 wing can have zero dihedral because the horizontal tail in combination with the ventral fins reduces the rolling moment of the vertical tail in a sideslip to the desired value.

Thanks for your detailed answer Peter.  Maybe this comment belongs to a separate question, but as far as I remember from F-4's tail structure, they also have anhedral tail wings.  Although its wings are not aligned in the same level, why F-4's have anhedral tail wings then?

@albin: If I remember correctly, it was to get more lateral area without increasing the fin. Working in the wake of the fuselage, the fin became worthless at higher angles of attack, and lack of directional stability required a limiter for the AoA at 23°. Post a question, and I can explain better :-)

The F-4 has a similar anhedral on its tail. The purpose is to give better manoeuvrability in high angle of attack scenarios. I suppose the same should be true for the F-16, as they frequently enter high angle of attack profiles.


text:
PoH says airplane climbs steeper at higher weight. Why? How?
Here's a puzzle. Looking at the PoH of my aircraft, it appears that the climb angle (distance to clear a 50 foot obstacle, starting from the end of the ground roll) is shallower at lower weight than at max gross.
That doesn't make sense to me - oughtn't the climb slope to be steeper at lower weight?
For example, the PoH claims that at sea level, 20 C and 1430 lb, the ground roll is 424 feet, and it needs 972 feet (total, including the ground roll) to clear a 50' obstacle.
At 1320 lb (also 20 C and sea level), it says ground roll is 210 feet and 782 feet to clear the 50 feet.
So the climb slope at 1430 lb is (972-424)/50, or 10.96:1.
And the climb slope at 1320 lb is (782-210)/50, or 11.44:1. Shallower, at lower weight.
I get similar results at all temperatures and pressure altitudes.
What's going on?

@RobertDiGiovanni PoH numbers are standardized; that's not how they work. The 972 feet to clear 50' is total, from being stopped. I'm pretty sure.

@MichaelHall Have a look for yourself: https://superpetrelusa.com/wp-content/uploads/2021/08/Pilot-Poerating-Handbook-Rotax-912.pdf page 5-3 is for 1430 lb, page 5-4 is for 1320 lb.

There are three stages to a short field takeoff over an obstacle- the ground roll, where the airplane accelerates to the minimum airspeed necessary to leave the ground, a period of further acceleration to Vx, and then a climb at Vx. I believe your analysis is flawed because it ignores this acceleration period.
The ground roll is the distance from the beginning of the takeoff run to the moment the airspeed is sufficient to become unstuck. When the aircraft is lighter, the required airspeed to become unstuck is less. So the heavier aircraft will be going faster at the end of the ground roll than the lighter aircraft will be.
The climb angle of the lighter aircraft is certainly steeper once both have reached Vx. But the lighter aircraft is further from Vx at the moment the ground roll ends and spends a little more distance accelerating to reach the same airspeed.

So, briefly, (972-424)/50 is an oversimplification.  "The" climb slope isn't constant from wheels up to obstacle cleared.

@Chris That makes sense, but Vx is itself lower at lower weight (altho this is not shown in the PoH). But I suppose you have to be correct.

@CamilleGoudeseune Right. Or to put it another way, lighter aircraft are better at climbing steeper but they're even more better at leaving the ground at low airspeeds.

@nerdfever.com True, but I'm not sure it's as big as a difference. More to the point, it's likely that the POH numbers are assuming that you are climbing at the published "Vx" not the true absolute best Vx corresponding to your actual weight. It would be rather a poor idea to publish required takeoff distances assuming you are traveling some airspeed they don't tell you how to calculate!

@Chris I think the PoH numbers are from actual flight tests, not calculated. So they don't even know exactly what Vx is at anything other than max gross weight.

@nerdfever.com They may or may not have run some tests to figure out Vx at other weights, but unless they've published them they certainly can't publish performance figures using them, is my point.

This is a very interesting question involving an amphibious aircraft, the Super Petrel LS.
Building on the answer by Chris, we see that take-off from water would involve "muddy/soft" field technique.
Indeed, the lighter plane would lift out of the water at a slower speed, therefore requiring more time to accelerate.
On dry land, it would be smarter to hold off on rotation until reaching Vx in any case, as rolling at low AoA is less draggy than flying.  Only when field conditions create greater drag is it advantageous to haul it into the air at a lower airspeed.
This is why many planes take off "clean", no flaps, using a greater ground roll and climb out at Vy.  Even at Vx with flaps, keeping drag as low as possible by delaying rotation can be the most efficient way to gain airspeed.

Very helpful. Is this true in general, that the best way to clear an obstacle is to rotate only when reaching Vx? I've heard rotating earlier is recommended, followed by accelerating in ground effect until Vx.


text:
How are flight hours counted?
I was watching a presentation from a software developers' conference in which the presenter went through the steps leading to the crash of United Airlines Flight 232 to make a point about Crew Resource Management and how it relates to software development.
This prompted me to read the above linked Wikipedia article and see mentions of the flight hours the captain and first officer had accumulated. Now the Wikipedia article on flight hours doesn't explain it, so I was wondering: how are these flight hours logged (and I don't mean on which medium)?

Are fractions of an hour taken into account or only ever full hours? I.e. if some pilot flew 1:27 h on one flight and 1:33 h on another how does that count towards the logged flight hours?
Given many regulations surrounding aviation seem to be global, is the way flight hours are logged uniform around the world?
Any differences between commercial, private and military aviation?

NB: I'm a layperson.

Originally my question also asked for this detail:

Is the time from the gate to the runway counted?

In regard to US regulations it's been answered here

Welcome to the site! Do you mean flight hours in the context of total experience in the cockpit, or flight hours for the purposes of crew rest?

@GdD phew ... frankly I meant the total experience in the cockpit, because I wasn't even aware of the distinction you mention.

@GdD I think that other Q&A answers the third point, right. Could you elaborate how the questions are different depending on the context and how I might improve on my existing question (or perhaps split it up)? The issue is that as a layperson I may lack the knowledge and terminology when it comes to these things, so your insights are much appreciated.

I think all of your questions are answered there, except the first. There's no set rule on that, most people round the time to the closest 5 minutes.

I can answer part of this by experience, as a non-professional hobbyist pilot, and partly by information which is fairly easy to come by. So here goes:

Are fractions of an hour taken into account or only ever full hours? I.e. if some pilot flew 1:27 h on one flight and 1:33 h on another how does that count towards the logged flight hours?

Fractions of hours are absolutely taken into account. Typically accuracy is not to the minute, as this would be fairly pointless but typical schemes are to round to the nearest 1/10th of an hour (6 minutes) or 5 minutes. Personally, a long time ago I chose to go for 5 minute rounding and have regretted it ever since - 6 minutes is much easier to add up when dealing with hours & minutes!

Given many regulations surrounding aviation seem to be global, is the way flight hours are logged uniform around the world?

Nothing in aviation is global, or very little. Although there are bodies such as ICAO (International Civil Aviation Organisation) which most member states tend to derive most of their rules from. For the purpose of logging flight time, I expect most civil pilots log on the basis of "Chock to chock" time. Which is to say when the aircraft moves under it's own power until it stops.

Any differences between commercial, private and military aviation?

From what I can tell, the only difference is military which seem to log in-air time. This, I'm told, is why military airmen who intend to pursue a commercial pilot career after they're discharged maintain a separate record of their flight time.

Thanks! So you'd round up always? And the separate record kept by military pilots would be kept according to the rules you outlined for civilian pilots, right?

There isn't a global standard, and even national regulations can be maddeningly vague, which is one of the reasons why this comes up often with new pilots or when moving to a different country.
For instance, the FAA only allows (though does not require) logging time that a pilot is "operating an aircraft for the purposes of flight."
General Aviation pilots generally uses Hobbs time, which is from engine start (or, depending on the wiring, from taxi start) to engine shutdown, because that's how most rental places charge.
Airline pilots generally use block time, which is from cabin door close to cabin door open, because that's how pilots are paid, so there are already automated systems recording that number and reporting it to them on their paychecks.
Military pilots log only time in the air. Since they're neither paying for nor getting paid for any specific flight, this is the simplest number.
Confusingly, an airline pilot who also flies GA and AF/ANG reserves on his days off will be logging flights under all three systems! Fortunately, the FAA accepts all three as valid interpretations, and perhaps these disparite practices are why their regulation on the matter is so vague in the first place.
As for accuracy, nearly everyone rounds to the nearest tenth of an hour, which also somewhat masks the differences between the systems.

AF/ANG == Air Force/Air National Guard?

@0xC0000022L Yes, I'm pretty sure that's what is meant there. Also, just so you're aware, while it's not required, normal practice on SE is to wait about a day before accepting an answer in case a better/more complete one shows up.

@reirab I'm aware. The limit is only 2 or 3 hours, though and if a considerably better answer shows up, I've also "switched" in the past (which is possible without much problem).

@reirab Just to explain. There's a reason I do this. I sometimes "lose sight" of a question for prolonged periods. So I'd rather accept a good answer than no answer, even if it later turns out there's an even better answer. It annoys me when questions have been objectively answered but remain marked as unanswered, because the inquirer doesn't bother to accept any answer. But in my experience answers that tend to be a lot better often don't appear until much later. So even the one day practice you paraphrase wasn't very effective for me in the past. But YMMV.

@0xC0000022L No problem, that makes sense. I originally just saw your rep here and didn't notice you had been around SO and other SE sites for a long time, so I thought you were a new user at first and was trying to help.

@reirab yep, and it's much appreciated. Having just asked my first question, I found this so far one of the most welcoming SE communities. There are others that are on par, but you only get to be a "new contributor" once per site, so it's fun to see it. And it's a pleasure to see this community so welcoming, when having experienced it quite differently on a few other SE sites. So thanks and


text:
What is an Air-Filed Flight Plan? Are aircraft capable of filing flight plan when in flight?
ICAO Doc 4444 mentions to input AFIL in the departure field of flight plan if it has been filed in the air. What is an Air-Filed flight plan? Can aircraft crew file a flight plan in-flight? If yes what are the equipment that support filing flight plans when in flight?

Are you specifically wanting international commercial operations? For GA in the US, all I have to do is call Flight Service (on an appropriate radio frequency) and tell them all the info, they file it for me.

Would you please define "AFIL"?  It might help us understand whether you asking about some sort of data link method vs simply using the radios as others have described.

AFIL is Air-Filed.

I don't think automation has quite reached the point where aircraft can file their own flight plans.

Welcome to aviation.SE! See this question and this one. Both those questions are about general (non-commercial) aviation in the US, is that what you're asking about?

Aircraft are not, on their own, capable of filing any sort of flight plan.

@jamesqf, not without human intervention of course, but the technology is definitely there to allow data link filing vs calling FSS on the radio.

@Michael Hall: But that is simply the human pilot using an electronic device to file, just as we humans are using computers to exchange these messages. (At least I think you're human: if not, you're a really good AI :-))  Having the aircraft file its own flight plan would be like having a completely self-driving car.

I completely agree.  I think we are just making the same point in subtly different ways.  This is where the OP can clarify what they are asking...

It is quite easy in the US but it depends on controller workload.  You need to be in a plane equipped for IFR flight and you need to be IFR current....[edit] to legally use a filed IFR flight plan.
If the controller is too busy they will make you file through a flight service station.  This can also be done in flight but requires you to change frequencies, reach the FSS, wait your turn, and then file.  The FSS puts you in the system.  Then you call ATC back and open your plan [edit] -or- open with the FSS.
If the controller has time, they will file you on frequency.

You can air file a VFR flight plan. I think the only kind of flight plan you can't file in the air is a DVFR or IFR crossing a border.

@RonBeyer That's exactly the pilot of an air-filed plan, it allows you to file a completely normal FPL from the air (including IFR)

@expeditedescent Yes, I know that. The answer here seems to make a suggestion that you must be in an IFR certified aircraft for that to happen, my point is that IFR is not a requirement for air-filed plans... I'm also fairly certain that FSS can open a flight plan, not just file it.

@RonBeyer Got it. Good point

@RonBeyer, can you think of a reason to file a VFR flight plan in the air? Usually the reason for filing a flight plan in the air is that you want to switch to IFR because the weather is getting worse faster than forecast/expected.

@JanHudec I can think of a few, for example if it's a nice day and on an IFR plan, but controller won't clear you direct, you can cancel IFR and go VFR. If you leave expecting flight following but don't get it... etc... But that isn't the point of the OP's question. You do not need to be IFR anything to air file a flight plan, only to file an IFR flight plan. You don't need to be IFR certified to file a VFR flight plan from the air, the reason for doing so is up to the pilot needing to do it, the system supports it.

To answer your question directly, the equipment enabling a pilot to file a flightplan while in the air is a radio. It is rarely needed, but air traffic control can file a flightplan submitted by a pilot over the radio. An air-filed flightplan is just that - a flightplan filed (via ATC) while an aircraft is in the air. It is a complete flightplan that lets you do all the same things a flightplan filed before departure does.
Note that landing at a different destination than the one filed in your flightplan does not require a pilot to file a flightplan from the air - diversions are handled by direct ATC coordination, without filing a new flightplan.

Of course nowadays any pilot flying a plane with WiFi could quite easily file a flightplan through an online flight planning service, which one might also (rightly) call an air-filed flightplan.


text:
Effect on pressure and/or volume of a real vs. ideal compressor
I'm looking at the Brayton cycle and trying to understand what happens when we move from the ideal cycle (isentropic compression/expansion) to the real world where we have adiabatic compression/expansion with associated compressor and turbine (in)efficiencies. I understand with adiabatic processes when compressor/turbine efficiencies are less than 1, that there is now an increase in entropy and an increase in temperature vs. the ideal cycle. My question is, with a higher temperature at the end of compression (and expansion), is there any associated change in the pressure and/or volume? Said another way, I'm struggling to square off the occurrence of a higher temperature at the end of compression, but is the pressure and/or volume higher as well?

If you don't get answer here, you might try https://physics.stackexchange.com/


text:
What is the direction convention for Roll angle?
This page from Wikipedia says:

A positive rolling motion lifts the left wing and lowers the right wing.

Which means that if an aircraft has a roll of +20 degrees, it would bank towards the right. And for a roll of -20 degrees, it would roll to the left.
But when I used this flight indicators library, for a roll of +20 degrees the attitude indicator showed that the aircraft was banking left and vice versa.
Are there any conventions for the roll angle/attitude indicator?

As someone who has actually worked on certifiable AHRS software, a positive roll is to the right. (Right wing down)

@selectstriker2, is it defined that way somewhere? I'm just curious where the convention comes from.

As someone who has actually worked with all sorts of simulation software, I say the sign convention in many libraries, particularly [those started as] amateur ones, can be anything. I've seen horrors like angles and angular rates having opposite sign convention. Of the popular ones, FSX/P3D has left roll positive. So a certain library is no authority, but expect anything. How it should be is written in Peter's answer; I'll just add that another common choice is forward-up-right (XYZ): it has convenient 'up' direction but yaw 'against' the compass. Either way, the system must be right-handed.

What I also noticed was, with the z-axis down convention, a positive roll increases the heading angle and vice versa. This way I don't have to change the sign for heading calculation.

@NeilPatrao RTCA DO-334 MOPS for Strapdown AHRS defines Roll as - The angle of rotation about the longitudinal axis of the aircraft. Roll
is defined as 0° when the aircraft is upright and the lateral axis is in
the level plane. It is defined as positive for the right wing of the
aircraft below the left wing.

That depends on the coordinate system, and the Wikipedia answer uses the most common convention. Flight mechanics uses a coordinate system with X in flight direction, Y sideways to the right and Z downwards positive. If you now apply the right-hand-rule for the positive direction of rotation around each axis, you will get a positive roll angle around X when the right wing moves down.

Right-hand-rule for rotation: Point the thumb in positive axis direction, then the other fingers will point into the positive direction of rotation.
If, however, X points backwards, then a positive roll angle would be as used in the linked library. Such a coordinate system is sometimes used to have Z point up, but is rather unusual for flight mechanics.

I was going to answer the same, but then I noticed that OP is asking about the indicator. I cannot find anything specific about it and I doubt that any would deviate from the norm, but is it written anywhere?

Curiously, the circular arrow in the diagram is visually ambiguous. It can be “seen” as either direction.

@JimGarrison: Well, the hand gives you a perspective from which the arrow should be viewed, and the finger direction is obvious. There is always a problem to represent 3D in two dimensions, but to misread the arrow takes some effort.

In that case, I'm gonna modify the library. Thanks for the explanation.

@Neil, be careful to change all rotations in a consistent manner! They are fully determined by the coordinate system, and if you use forward-right-down, not only positive roll will be right, but positive pitch - up, positive yaw - right. Nothing is worse than an inconsistent arbitrary choice of conventions.

I can easily flip my perception either way. Making the thickness of the circle continuously vary so it is thinner (ie farther away) where it crosses the straight line would provide the necessary visual clue.

RTCA DO-334 Minimum Operational Performance Standards for Strapdown AHRS defines pitch, roll, and heading as the following:

Pitch
The angle between local level and the longitudinal axis of the
aircraft. It is defined as positive for the nose of the aircraft pointing
above local level.
Roll
The angle of rotation about the longitudinal axis of the aircraft.
Roll is defined as 0° when the aircraft is upright and the lateral
axis is in the level plane. It is defined as positive for the right
wing of the aircraft below the left wing.
Heading
The relative angle between the projection of the longitudinal axis of
the aircraft onto the local level frame and some definition of North,
for example either True North or Magnetic North. Heading is
positive for angles clockwise from (east of) North.

This corresponds to using the right hand rule with the positive axes forward, right, and down.